During certain sporting events, and in particular during basketball matches or other team sports governed by the same type of playing time rules as basketball, it is common practice that each time a stoppage is called by one of the referees, usually the head referee, or the only referee present, the playing time countdown is stopped. In this way, only actual periods of play are taken into account to assess the playing time for the game in progress, and interruptions due in particular to replacements of players, injuries, fouls, etc. are not counted against the playing time.
These sporting events are thus subject to the stopwatch or chronometer, which traditionally counts down the playing time, and any referee intervention must cause that stopwatch to be stopped from counting down the playing time, in other words to avoid taking these interruptions in the game into account in the overall playing time allocated for the game in progress.
In many cases, the referee signals the stop of the playing time by blowing a whistle; the whistle generally being duly approved and referenced by the federation in charge of these sporting events or any other sworn organization for these sporting events. It is also possible for this same referee to signal the resumption of playing time by blowing this same whistle, which then triggers the start or restart of the stopwatch.
In certain sports, such as basketball, the playing phases are particularly quick and broken up, with many play stoppages during the match, such that forgetting or delays in stopping the stopwatch are regular and cause disputes that are always delicate for the referees to resolve.
To respond to this issue, it is known to use systems for automatically detecting the blowing of the whistle and stopping the stopwatch. It is thus known from document EP 0 712 508 B1 to use a remotely controlled timing installation that includes:                several portable systems each provided, on one hand, with a microphone that measures external sounds and delivers raw analog measuring signals and, on the other hand, a remote controlled portable transmitter that transmits these raw measuring signals; and        a fixed system comprising a radio receiver placed on the scoreboard, in radio connection with the remote controlled portable transmitters, followed by a mixer that mixes the raw analog measuring signals, then a high-pass filter and low-pass filter assembly, then an electronic control circuit that delivers a switching signal intended for the stopwatch.        
The connection between the portable systems and the fixed system is thus done using an analog radio transmission, in modulated frequency, in frequencies selected to be separate from the transmission frequencies of the external electronic equipment such as television cameras, equipment for communicating with the security team, etc.
The detection of the whistle is done in the fixed system, in other words at the scoreboard, in particular using a high-pass filter whereof the cutoff frequency corresponds substantially to the whistle transmission frequency, so as to allow frequencies higher than the cutoff frequency (or whistle frequency) to pass and attenuate frequencies below the cutoff frequency.
However, this type of remote controlled stopwatch installation has many drawbacks due primarily to the analog radio connection between the portable systems and the fixed system.
Indeed, this analog radio connection deforms and colors the transmitted analog signals and modifies the signature thereof, thereby affecting the reliability of their detection.
Indeed, the components used for the transmission, the transmission and the analysis of the analog signals have unique characteristics (bandwidth, distortion, different filtering effects, etc.), which permanently modify the analog signal. The system is then said to color the analog signal, in other words to modify the spectral response of said analog signal. Each transformation of the analog signal generated by these components necessarily generates background noise because each component creates some. The major drawback of an analog system is the irreversible degradation of the analog signal, the system being incapable of distinguishing the useful signal from the background noise.
Thus, the wireless radio being analog, there is no means for recapturing a communication if it is scrambled, or even of detecting the failure of the system such that, on one hand, whistles cannot be detected by the fixed system following electromagnetic disruptions caused by external electronic apparatuses and, on the other hand, these same external electronic apparatuses can disrupt the transmitted analog signal to the point of erroneously triggering the stoppage of the playing time.
Moreover, in the case of the installation disclosed in document EP 0 712 508 B1, the detection of the whistle is done after the scoreboard radio receiver, with a simple band-pass analog filtering that is intended to detect the frequency of the whistle. It has, however, been observed, with this type of installation, that any acoustic signal having a frequency component of the same nature, such as for example whistles belonging to the general public, the screech of shoe soles on the ground, etc. is interpreted as a whistle, thereby triggering an undesired stoppage of the stopwatch.
Thus, this installation using analog communication systems has a lack of reliability that is sometimes crippling, as it is a source of conflicts between the teams and referees, when the whistles transmitted by the referee are not detected and when external sounds (whistles belonging to the general public, screeching of shoe soles, etc.) erroneously trigger the stoppage of the stopwatch.
Some systems, approximately similar to the one described into document EP 0 712 508 B1, are also known from documents U.S. Pat. No. 5,065,251, U.S. Pat. No. 3,651,507, SU 1409301 A1, FR 2 387 479 A and PT 97 522.